An optical printer is a device consisting of one or more film projectors mechanically linked to a movie camera. It allows filmmakers to re-photograph one or more strips of film. The optical printer is used for making visual effects for motion pictures, or for copying and restoring film material. [1]
Common optical effects include fade outs and fade ins, dissolves, slow motion, fast motion, and matte work. More complicated work can involve dozens of elements, all combined into a single scene.
The first commercially available, although not mass produced, optical printer appeared in 1927 and was called the Depue & Vance Daylight Optical Printer. It was mainly used to reduce standard prints to 16mm and allowed for operation without a darkroom except for loading the positive film magazine. In 1918, the cinematographer Carl Gregory came upon a printer made by G. J. Badgley of New York, designed to produce copies of a standard film using domestic size film stock. Realizing the potential for news productions and special effects, he started designing his own optical printer meant for movie effects. Finished in 1928, and built by Fred A. Barber, it could be used in 16 different ways, like alongside fades, superimposition and multiple exposures. [2] Linwood G. Dunn expanded the concept in the 1930s by creating an optical printer that eliminated the necessity to create optical effects in the camera, and which was used in King Kong . [3] These first optical printers had to be individually developed by each movie studio. During World War II he was commissioned by the United States armed forces' photographic units to design an optical printer that could be ordered as a stock item like a camera. Named the Acme-Dunn optical printer, it had several new features compared to its predecessors, but was not made commercially available for the movie industry after the war. [4] [5]
Development continued well into the 1980s, when the printers were now controlled using minicomputers. [6] Prime examples of optical printing work include the matte work in Star Wars (1977), [7] RoboCop (1987) and The Addams Family (1991). [8] The film Who Framed Roger Rabbit (1988) involved over 1,000 shots that required optical printers, due to the film's combination of live action and cartoon elements. Some shots, such as those featuring Jessica Rabbit, involved as many as thirty layers of film. [9]
At Lucasfilm, the Graphics Group was working to come up with a digital version of the optical printer. They invented the Pixar Image Computer, which could both handle digital compositing and simulate analog effects, while David DiFrancesco developed a laser scanner that could transfer the images from the computer to film. [10] In the late 80s, the digital compositing had begun to supplant optical effects. By the mid-nineties, computer graphics had evolved to rival and surpass what was possible with optical printers, and many now consider optical printing all but obsolete. [11] Improvements in film scanners and recorders allow for a complete feature film to be processed by computers, have special effects applied, and then be processed back to film.
Today, optical printing is mostly used as an artistic tool by experimental film makers, for educational purposes, or for photochemical (as opposed to digital) film restoration. As a technique, it is particularly useful for making copies of hand painted or physically manipulated film. [12]
As in any analog process, every re-printing degrades the picture, just like a photocopy of a photocopy. Properly performed contact printing generally creates less degradation provided that the contact between the negative and the print film is perfect. Optical printing can emphasize the grain structure and any imperfections in the negative. [13] Also, since a new, different piece of film was exposed and printed, matching the exact colors of the original was a problem. Often the printer work was limited to only the parts of a dissolve needing the effect. The original footage was spliced mid-shot with the optically-printed portion, often resulting in an obvious change in image quality when the transition occurs.
Other problematic artifacts depend on the effect attempted, most often alignment inaccuracies in matte work. For this reason, shots intended to be manipulated via optical printer were often shot on larger film formats than the rest of the project. Otherwise obsolete formats, such as VistaVision, remained in use for many years after they had been abandoned for the conventional shooting of scenes because their larger frame size provided greater clarity, reduced grain size when reprinted and any alignment problems were not as conspicuous.
Optical printers have often been used in the recovery of older, damaged film stock which includes the 1989 restoration of Intolerance (1916). [8]
Scratches, abrasions, cinch marks caused by rewinding a film too tightly, and other blemishes are a common problem with films that are candidates for restoration. Most of these scratches are in the back side of the film in the transparent substrate that forms the film base, rather than in the photographic emulsion on the front that holds the film's actual image. [14] In the normal process of duplicating a film in an optical printer, collimated light passes through the film base on its way to illuminate the emulsion. Any scratches, abrasions, etc., in the film base cause the light to bend such that the duplicated film ends up with bright or dark (depending on whether copying from a negative or positive original) copies of the scratches. This bending of the light is being caused by the difference in the refraction index of the substrate and the air. [15]
If these scratches and abrasions can be prevented from being captured on the new print, it eliminates one entire area of restoration work. Three methods address this problem. First, one can simply enlarge the portion of the film not damaged. This mainly has application where the damage is confined to the edges.
The second method is wet-gate printing. The "gate" in a projector is the apparatus that holds the film in place as each frame is shown. A wet gate is filled with a fluid that coats the film as it is fed through, constantly replenishing the fluid as needed. [15]
Wet gate printing eliminates the refraction itself by filling in the gouges in the substrate with a fluid such as perchloroethene that shares approximately the same refractive index as the substrate. With the fluid temporarily displacing the air in the scratches and abrasions, refraction simply no longer occurs, so the defects are not reflected on the new copy. The light used is fully collimated, as with standard optical printing, and the film is undamaged by the process. [14] [16] This method does not work if the scratches on the emulsion side are deep enough to have removed some of the silver or dye image in the original film.
The third method involves inserting a diffusion filter in the path from the collimated light source to the film. It can eliminate the projection of small defects on the back side of the film onto the new copy because the light, rather than arriving at the back of the film in perfect parallel lines, instead enters the scratch from several directions. It is therefore still diffuse when it exits, ensuring an image of the scratch will not show up as strongly on the new print. (Only the desired image on the surface of the emulsion ends up being captured in focus.) [14] This method results in the most finely-focused capture of the original. [17] However, it cannot remove deep scratches, and is thus less effective than wet gate printing.
Lithography is a planographic method of printing originally based on the immiscibility of oil and water. The printing is from a stone or a metal plate with a smooth surface. It was invented in 1796 by the German author and actor Alois Senefelder and was initially used mostly for musical scores and maps. Lithography can be used to print text or images onto paper or other suitable material. A lithograph is something printed by lithography, but this term is only used for fine art prints and some other, mostly older, types of printed matter, not for those made by modern commercial lithography.
A mimeograph machine was a low-cost duplicating machine that worked by forcing ink through a stencil onto paper. The process was called mimeography, and a copy made by the process was a mimeograph.
Screen printing is a printing technique where a mesh is used to transfer ink onto a substrate, except in areas made impermeable to the ink by a blocking stencil. A blade or squeegee is moved across the screen to fill the open mesh apertures with ink, and a reverse stroke then causes the screen to touch the substrate momentarily along a line of contact. This causes the ink to wet the substrate and be pulled out of the mesh apertures as the screen springs back after the blade has passed. One colour is printed at a time, so several screens can be used to produce a multi-coloured image or design.
Chroma key compositing, or chroma keying, is a visual-effects and post-production technique for compositing (layering) two or more images or video streams together based on colour hues. The technique has been used in many fields to remove a background from the subject of a photo or video – particularly the newscasting, motion picture, and video game industries. A colour range in the foreground footage is made transparent, allowing separately filmed background footage or a static image to be inserted into the scene. The chroma keying technique is commonly used in video production and post-production. This technique is also referred to as colour keying, colour-separation overlay, or by various terms for specific colour-related variants such as green screen or blue screen; chroma keying can be done with backgrounds of any colour that are uniform and distinct, but green and blue backgrounds are more commonly used because they differ most distinctly in hue from any human skin colour. No part of the subject being filmed or photographed may duplicate the colour used as the backing, or the part may be erroneously identified as part of the backing.
Inkjet printing is a type of computer printing that recreates a digital image by propelling droplets of ink onto paper and plastic substrates. Inkjet printers were the most commonly used type of printer in 2008, and range from small inexpensive consumer models to expensive professional machines. By 2019, laser printers outsold inkjet printers by nearly a 2:1 ratio, 9.6% vs 5.1% of all computer peripherals.
Special effects are illusions or visual tricks used in the theatre, film, television, video game, amusement park and simulator industries to simulate the imagined events in a story or virtual world. It used to be called SFX but this short form has also expanded to include “sound effects” as well.
Schlieren photography is a process for photographing fluid flow. Invented by the German physicist August Toepler in 1864 to study supersonic motion, it is widely used in aeronautical engineering to photograph the flow of air around objects.
Visual effects is the process by which imagery is created or manipulated outside the context of a live-action shot in filmmaking and video production. The integration of live-action footage and other live-action footage or CGI elements to create realistic imagery is called VFX.
Digital printing is a method of printing from a digital-based image directly to a variety of media. It usually refers to professional printing where small-run jobs from desktop publishing and other digital sources are printed using large-format and/or high-volume laser or inkjet printers.
Offset printing is a common printing technique in which the inked image is transferred from a plate to a rubber blanket and then to the printing surface. When used in combination with the lithographic process, which is based on the repulsion of oil and water, the offset technique employs a flat (planographic) image carrier. Ink rollers transfer ink to the image areas of the image carrier, while a water roller applies a water-based film to the non-image areas.
The gelatin silver process is the most commonly used chemical process in black-and-white photography, and is the fundamental chemical process for modern analog color photography. As such, films and printing papers available for analog photography rarely rely on any other chemical process to record an image. A suspension of silver salts in gelatin is coated onto a support such as glass, flexible plastic or film, baryta paper, or resin-coated paper. These light-sensitive materials are stable under normal keeping conditions and are able to be exposed and processed even many years after their manufacture. The "dry plate" gelatin process was an improvement on the collodion wet-plate process dominant from the 1850s–1880s, which had to be exposed and developed immediately after coating.
Security printing is the field of the printing industry that deals with the printing of items such as banknotes, cheques, passports, tamper-evident labels, security tapes, product authentication, stock certificates, postage stamps and identity cards. The main goal of security printing is to prevent forgery, tampering, or counterfeiting. More recently many of the techniques used to protect these high-value documents have become more available to commercial printers, whether they are using the more traditional offset and flexographic presses or the newer digital platforms. Businesses are protecting their lesser-value documents such as transcripts, coupons and prescription pads by incorporating some of the features listed below to ensure that they cannot be forged or that alteration of the data cannot occur undetected.
Compositing is the process or technique of combining visual elements from separate sources into single images, often to create the illusion that all those elements are parts of the same scene. Live-action shooting for compositing is variously called "chroma key", "blue screen", "green screen" and other names. Today, most, though not all, compositing is achieved through digital image manipulation. Pre-digital compositing techniques, however, go back as far as the trick films of Georges Méliès in the late 19th century, and some are still in use.
A minilab is a small photographic developing and printing system or machine, as opposed to large centralized photo developing labs. Many retail stores use film or digital minilabs to provide on-site photo finishing services.
Mattes are used in photography and special effects filmmaking to combine two or more image elements into a single, final image. Usually, mattes are used to combine a foreground image with a background image. In this case, the matte is the background painting. In film and stage, mattes can be physically huge sections of painted canvas, portraying large scenic expanses of landscapes.
In cinematography, bipacking, or a bipack, is the process of loading two reels of film into a camera, so that they both pass through the camera gate together. It was used both for in-camera effects and as an early subtractive colour process.
Inkjet paper is a special fine paper designed for inkjet printers, typically classified by its weight, brightness and smoothness, and sometimes by its opacity.
A wet-transfer film gate, or wet gate for short, is a film gate that is submerged in liquid, used for film restoration and archival scanning. Submerging the film in the gate in a liquid with a suitably matched refractive index reduces the effects of scratches on the film, by reducing the refractive effects which divert light that passes through the scratched part of the film. The liquid also acts to lift other forms of defects from the film. Perchloroethylene, a hazardous substance with multiple health and safety risks, is commonly used as the liquid medium in wet gate systems, requiring substantial precautions to be taken to ensure the safety of operators and to prevent pollution.
A contact copier is a device used to copy an image by illuminating a film negative with the image in direct contact with a photosensitive surface. The more common processes are negative, where clear areas in the original produce an opaque or hardened photosensitive surface, but positive processes are available. The light source is usually an actinic bulb internal or external to the device
The Williams process or Williams doublematting process is a matte creation technique patented by the American cinematographer Frank D. Williams in 1918. Unlike prior matte techniques, it allowed for the integration of the actors' movements with previously shot backgrounds.